The root cause is the controllable underlying cause which, when eliminated, prevents the problem from recurring. This is its difference from a symptom: intervening in the symptom hides the problem temporarily, intervening in the root cause closes it permanently.
Two separate chains must be followed in the analysis. The occurrence cause explains why the problem arose. The escape cause explains why the existing control system failed to catch the problem. An analysis that focuses on only one of them is incomplete.
Statements such as “operator carelessness” are usually not a root cause but a point where the analysis stopped early. What should be asked is how the error was possible and why it was not noticed.
Related terms: Corrective Action · Nonconformity · Horizontal Deployment
Related training: Structured Problem Solving and Root Cause Analysis